Structural body and method for producing the same

Abstract

A structural body includes a tubular insulating body having a hollow portion and a conducting body inserted into the hollow portion in the insulating body, and the insulating body and the conducting body are directly integrated with each other by firing. In a tensile test in which the insulating body is fixed, and a portion of the conducting body that protrudes from the insulating body is pulled in the axial direction, the displacement of the conducting body with respect to the insulating body is 5% or less of the axial direction length of the contact portion between the hollow portion and the conducting body under a tensile load per unit contact area between the insulating body and the conducting body of 0.05 kgf/mm 2 or less.

What is claimed is: 
     
         1 . A structural body comprising a tubular insulating body having a hollow portion and a conducting body inserted into the hollow portion, the insulating body and the conducting body being directly integrated with each other by firing,
 wherein in a tensile test in which the insulating body is fixed, and a portion of the conducting body that protrudes from the insulating body is pulled in an axial direction, a displacement of the conducting body with respect to the insulating body is 5% or less of an axial direction length of a contact portion between the hollow portion and the conducting body under a tensile load per unit contact area between the insulating body and the conducting body of 0.05 kgf/mm 2  or less.   
     
     
         2 . The structural body according to  claim 1 , wherein in a withstand voltage test in which two of the structural bodies having the same shape are prepared and arranged parallel to each other, a distance between the arranged structural bodies being twice as large as a thickness of the insulating body, a direct voltage is applied between the structural bodies, and the applied voltage is gradually increased, the structural bodies do not cause insulation breakdown even if an average electric field applied between the structural bodies reaches 10 kV/mm. 
     
     
         3 . The structural body according to  claim 1 , wherein the structural body satisfies the following relational expression (1): 
       
         
           
             
               
                 
                   
                     
                       
                         
                           
                             
                               
                                 
                                    
                                   
                                     
                                       α 
                                        
                                       
                                           
                                       
                                        
                                       i 
                                     
                                     - 
                                     
                                       α 
                                        
                                       
                                           
                                       
                                        
                                       c 
                                     
                                   
                                    
                                 
                                  
                                 
                                   [ 
                                   
                                     × 
                                     
                                       
                                         10 
                                         
                                           - 
                                           6 
                                         
                                       
                                       / 
                                       K 
                                     
                                   
                                   ] 
                                 
                               
                               × 
                               
                                 10 
                                 
                                   - 
                                   6 
                                 
                               
                               × 
                             
                           
                         
                         
                           
                             
                               Δ 
                                
                               
                                   
                               
                                
                               
                                 T 
                                  
                                 
                                   [ 
                                   K 
                                   ] 
                                 
                               
                               × 
                               
                                 Ec 
                                  
                                 
                                   [ 
                                   GPa 
                                   ] 
                                 
                               
                               × 
                               
                                 Ei 
                                  
                                 
                                   [ 
                                   GPa 
                                   ] 
                                 
                               
                             
                           
                         
                       
                       
                         
                           ( 
                           
                             Ec 
                             + 
                             Ei 
                           
                           ) 
                         
                          
                         
                           [ 
                           GPa 
                           ] 
                         
                       
                     
                     ≦ 
                     
                       3 
                       × 
                       
                         Si 
                          
                         
                           [ 
                           GPa 
                           ] 
                         
                       
                     
                   
                 
                 
                   
                     ( 
                     1 
                     ) 
                   
                 
               
             
           
         
       
       where αi represents a thermal expansion coefficient of the insulating body, αc represents a thermal expansion coefficient of the conducting body, ΔT represents a difference between the firing temperature and a room temperature, Ec represents a Young's modulus of the conducting body, Ei represents a Young's modulus of the insulating body, and Si represents a flexural strength of the insulating body. 
     
     
         4 . The structural body according to  claim 3 , wherein the thermal expansion coefficient αi of the insulating body and the thermal expansion coefficient αc of the conducting body satisfy the relation of:
   1[×10 −6 /K]≦(α i−αc )≦8[×10 −6 /K].
 
 
     
     
         5 . The structural body according to  claim 1 , wherein the conducting body is made of a material containing a substance selected from the group consisting of molybdenum, tungsten, silver, copper, nickel, and alloys containing at least one thereof. 
     
     
         6 . The structural body according to  claim 1 , wherein the insulating body is made of a composite oxide or composite nitride containing one or more substances selected from the group consisting of barium oxide, bismuth oxide, titanium oxide, zinc oxide, neodymium oxide, titanium nitride, aluminum nitride, silicon nitride, alumina, silica, and mullite. 
     
     
         7 . The structural body according to  claim 1 , wherein the structural body is used for an electrode for dielectric-barrier discharge. 
     
     
         8 . The structural body according to  claim 1 , wherein the structural body is used for an electrode for dielectric-barrier discharge in an ozone generator. 
     
     
         9 . The structural body according to  claim 1 , wherein:
 the insulating body has an extruded shape with the hollow portion being formed as a through-hole; and   the conducting body is a rod-shaped bulk conducting body inserted into the hollow portion in the insulating body.   
     
     
         10 . A method for producing a structural body comprising a tubular insulating body having a hollow portion and a conducting body inserted into the hollow portion, the insulating body and the conducting body being directly integrated with each other by firing, wherein in a tensile test in which the insulating body is fixed, and a portion of the conducting body that protrudes from the insulating body is pulled in an axial direction, a displacement of the conducting body with respect to the insulating body is 5% or less of an axial direction length of a contact portion between the hollow portion and the conducting body under a tensile load per unit contact area between the insulating body and the conducting body of 0.05 kgf/mm 2  or less, the method comprising:
 a green-body preparation step of preparing a green body to be formed into the insulating body, the green body having a hollow portion;   a preliminarily-fired body preparation step of degreasing and preliminarily-firing the green body to prepare a preliminarily-fired body;   a conducting body insertion step of inserting a bulk conducting body into a hollow portion in the preliminarily-fired body; and   a firing/integration step of firing the preliminarily-fired body together with the bulk conducting body inserted thereinto to produce the structural body.   
     
     
         11 . The method according to  claim 10 , wherein in the green-body preparation step, the green body is formed into an extruded shape. 
     
     
         12 . The method according to  claim 10 , wherein in the preliminarily-fired body preparation step, the green body is degreased and preliminarily-fired in an air atmosphere at a temperature lower than a firing temperature of the firing/integration step. 
     
     
         13 . The method according to  claim 10 , wherein in the firing/integration step, the preliminarily-fired body is fired in an oxygen-free atmosphere at a temperature higher than a degreasing/preliminary-firing temperature of the preliminarily-fired body preparation step. 
     
     
         14 . The method according to  claim 10 , wherein in the green-body preparation step, a starting material slurry containing at least a starting material powder and a dispersion medium is shaped and solidified to prepare the green body. 
     
     
         15 . The method according to  claim 14 , wherein the starting material slurry contains, as an organic binder, a gelling agent that is hardened by a chemical reaction. 
     
     
         16 . A method for producing a structural body comprising a tubular insulating body having a hollow portion and a conducting body inserted into the hollow portion, the insulating body and the conducting body being directly integrated with each other by firing, wherein in a tensile test in which the insulating body is fixed, and a portion of the conducting body that protrudes from the insulating body is pulled in an axial direction, a displacement of the conducting body with respect to the insulating body is 5% or less of an axial direction length of a contact portion between the hollow portion and the conducting body under a tensile load per unit contact area between the insulating body and the conducting body of 0.05 kgf/mm 2  or less, the method comprising:
 a green-body preparation step of preparing a green body to be formed into the insulating body, the green body having a hollow portion;   a conducting body insertion step of inserting a bulk conducting body into the hollow portion in the green body; and   a firing/integration step of firing the green body together with the bulk conducting body inserted thereinto to produce the structural body.   
     
     
         17 . The method according to  claim 16 , wherein in the firing/integration step, the green body is fired in an atmosphere containing a small amount of oxygen. 
     
     
         18 . The method according to  claim 16 , wherein in the green-body preparation step, a starting material slurry containing at least a starting material powder and a dispersion medium is shaped and solidified to prepare the green body. 
     
     
         19 . The method according to  claim 18 , wherein the starting material slurry contains, as an organic binder, a gelling agent that is hardened by a chemical reaction.